U.S. patent application number 11/683145 was filed with the patent office on 2007-09-13 for radiation imaging apparatus and radiation imaging system.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Tadao Endo, Toshio Kameshima, Katsuro Takenaka, Tomoyuki Yagi, Keigo Yokoyama.
Application Number | 20070210258 11/683145 |
Document ID | / |
Family ID | 38477990 |
Filed Date | 2007-09-13 |
United States Patent
Application |
20070210258 |
Kind Code |
A1 |
Endo; Tadao ; et
al. |
September 13, 2007 |
RADIATION IMAGING APPARATUS AND RADIATION IMAGING SYSTEM
Abstract
A radiation imaging apparatus comprises a read unit reading the
electric signal in the radiation detecting elements in a radiation
detecting unit comprises the radiation detecting elements
converting incident radiation into electric signals arranged
two-dimensionally, a control unit controlling the radiation
detecting unit with such that a first radiation detecting element
group is made senseless state and a second radiation detecting
element group is made sensible state, and a signal processing unit
performing a subtraction processing such that the electric signal
in the radiation detecting elements made senseless state read by
the read unit is subtracted from the electric signal in the
radiation detecting elements made sensible state read by the read
unit according to the state control by the control unit, to reduce
conspicuous line noise in an image by a relatively simple
configuration.
Inventors: |
Endo; Tadao; (Honjo-shi,
JP) ; Kameshima; Toshio; (Kumagaya-shi, JP) ;
Yagi; Tomoyuki; (Honjo-shi, JP) ; Takenaka;
Katsuro; (Kodama-gun, JP) ; Yokoyama; Keigo;
(Honjo-shi, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Assignee: |
CANON KABUSHIKI KAISHA
Ohta-ku
JP
|
Family ID: |
38477990 |
Appl. No.: |
11/683145 |
Filed: |
March 7, 2007 |
Current U.S.
Class: |
250/370.09 ;
250/370.11 |
Current CPC
Class: |
H04N 5/374 20130101;
G01T 1/247 20130101; H04N 5/32 20130101; H04N 5/3658 20130101; G01T
7/005 20130101 |
Class at
Publication: |
250/370.09 ;
250/370.11 |
International
Class: |
G01T 1/24 20060101
G01T001/24 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 10, 2006 |
JP |
2006-066089 |
Jan 17, 2007 |
JP |
2007-008140 |
Claims
1. A radiation imaging apparatus comprising: a radiation detecting
unit in which pixels including radiation detecting elements
converting incident radiation into electric charges are arranged
two-dimensionally; a control unit performing such a state control
that a first pixel in the radiation detecting unit is made
senseless state so that an electric charge generated in a first
radiation detecting element according to incident radiation cannot
be taken out of the first pixel and a second pixel different from
the first pixel is made sensible state so that an electric charge
generated in a second radiation detecting element according to
incident radiation can be taken out of the second pixel; and a
signal processing unit performing a subtraction processing such
that the electric signal read out from the second pixel made
senseless state is subtracted from the electric signal read from
the first pixel made sensible state according to the state control
by the control unit.
2. The radiation imaging apparatus according to claim 1 further
comprising a voltage supply unit supplying at least a first or a
second voltage to the radiation detecting elements of the radiation
detecting unit and the control unit causes the voltage supply unit
to supply the first voltage to the first radiation detecting
element and supply the second voltage to the second radiation
detecting element to perform the state control.
3. The radiation imaging apparatus according to claim 2, wherein
the voltage supply unit is provided with a first power source unit
connected to the first radiation detecting element and the second
power source unit connected to the second radiation detecting
element and the first and the second power source unit are provided
with their respective switching units changing over the first and
the second voltage, and the control unit performs such a control
that the switching unit of the first power source unit is thrown to
the position of the first voltage and the switching unit of the
second power source unit is thrown to the position of the second
voltage.
4. The radiation imaging apparatus according to claim 1, wherein
the control unit makes the pixels in the odd columns senseless
state and the pixels in the even columns sensible state, among the
pixels in the radiation detecting unit, or contrary to the above,
the control unit makes the pixels in the odd columns sensible state
and the pixels in the even columns senseless state, among the
pixels in the radiation detecting unit.
5. The radiation imaging apparatus according to claim 1, wherein
the control unit makes the pixels in one column senseless state and
the pixels in the other columns except the one column sensible
state, among the pixels in the radiation detecting unit.
6. The radiation imaging apparatus according to claim 1, wherein
the pixels are provided with a plurality of switch elements for
transferring the electric signals in the radiation detecting
elements to outside corresponding to the radiation detecting
elements, the radiation imaging apparatus further comprising a
drive circuit which drives the switch elements.
7. The radiation imaging apparatus according to claim 6, wherein
the drive circuit is connected to a plurality of drive wirings
connecting the switch elements in the line direction and
simultaneously drives the switch elements in a plurality of lines
through the drive wirings to read the addition of the electric
signals of a plurality of the radiation detecting elements on a
column basis.
8. The radiation imaging apparatus according to claim 6, wherein
the drive circuit comprises a first drive circuit which drives the
switch elements provided corresponding to the radiation detecting
elements in a certain column and a second drive circuit which
drives the switch elements provided corresponding to the radiation
detecting elements in the other columns except the certain column,
and the control unit causes one of the first and the second drive
circuit to drive and prohibits the other from driving to perform
the state control.
9. The radiation imaging apparatus according to claim 6, wherein
the pixels are provided with a plurality of switch elements for
transferring the electric signals in the radiation detecting
elements to outside corresponding to the radiation detecting
elements, the signal processing unit includes a read unit reading
an electric signal from the radiation detecting unit, and the
control unit performs the state control according to the control
provided for the read unit.
10. The radiation imaging apparatus according to claim 1, wherein
the radiation detecting element comprises a phosphor converting the
incident radiation into light and a photoelectric conversion
element converting the light converted by the phosphor into the
electric signal.
11. The radiation imaging apparatus according to claim 10, wherein
the photoelectric conversion element is containing as a main
ingredient amorphous silicon.
12. The radiation imaging apparatus according to claim 1, wherein,
in a moving image radiographing mode, the control unit performs
such a state control that a first pixel group in the radiation
detecting unit is made senseless state so that an electric charge
generated in the first radiation detecting element according to
incident radiation cannot be taken out of the first pixel group and
a second pixel group except the first pixel group is made sensible
state so that an electric charge generated in the second radiation
detecting element according to incident radiation can be taken out
of the second pixel group and the signal processing unit performs a
subtraction processing in which the electric signal read from the
radiation detecting element made senseless state by the read unit
is subtracted from the electric signal read from the radiation
detecting element made sensible state by the read unit according to
the state control by the control unit, in a still image
radiographing mode, the control unit performs such a control that
all the radiation detecting elements in the radiation detecting
unit are made sensible state and the signal processing unit does
not perform the subtraction processing.
13. A radiation imaging system comprising: the radiation imaging
apparatus according to claim 1; and a radiation source radiating
the radiation imaging apparatus with radiation.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a radiation imaging
apparatus and a radiation imaging system suitably applicable to
medical diagnosis and industrial non-destructive inspection. In the
description of the specification, a radiation includes
electromagnetic waves such as X- and gamma rays and alpha and beta
rays.
[0003] 2. Description of the Related Art
[0004] Nowadays, X-ray imaging in a hospital has been changing from
a conventional analog system using films to a digital system.
Digitized X-ray imaging easily solves problems which have been
pointed out so far such as the safekeeping of films, the management
of developers, radiographing time period and burden to patients at
the time of failure in radiographing and enables providing a new
medial environment to meet the needs of the times.
[0005] A CR (computed radiography) system using photostimulable
phosphor called an imaging plate (IP) as a digital X-ray imaging
system has dominated since 1980s and has had a share in
digitization. The CR system has indeed an aspect of digitization,
but it requires two-step process in which a latent X-ray image in
the IP by X-ray imaging is scanned by laser beams to obtain images.
For this reason, the CR system has still a problem with work flow
in that time is needed from radiographing to acquiring images.
[0006] A digital X-ray imaging apparatus provided with
radiographing detecting elements containing as a main ingredient
amorphous silicon and amorphous selenium have been practically used
in recent years. The former is of indirect type in which X-ray
images are converted into visible images by a phosphor containing
as a main ingredient CsI:TI or Gd.sub.2O.sub.2S:Tb and the visible
images are converted into electric signals by X-ray detecting
elements containing as a main ingredient amorphous silicon. On the
other hand, the latter is of direct type in which X-rays are
directly converted into electric signals by X-ray detecting
elements containing as a main ingredient amorphous selenium. Both
are capable of realizing a wider and thin X-ray imaging apparatus,
so that it is also referred to as "flat panel detector (FPD)" and
characterized in that the time required from imaging to observing
images is very short. In a recent digital system, a demand for the
CR system is still active, but a demand for the FPD system is
gradually developing.
[0007] In the next place, a moving image radiographing
(fluoroscopic radiography) is briefly described below. In
fluoroscopic radiography for gastric as an example of the moving
image radiographing, the inner wall of a stomach or duodenum with
barium swallowed as a contrast medium is observed by an imaging
apparatus called an image intensifier (II). The II is very
sensitive and a device widely used for moving image radiographing.
The II converts an X-ray image into a visual image and then
converges the visual image using an electronic lens, which offers a
drawback in that an apparatus becomes bulky and heavy and
peripheral images are greatly distorted. In addition, it is pointed
out that the II is so small in dynamic range that a problem with
halation is caused. Furthermore, the II remarkably deteriorates in
its characteristics and is short in lifetime, so that it needs to
be replaced every three to five years depending on frequency in
use. In a fluoroscopic radiographing for gastric, when a still
image is photographed by fluoroscoping by the II with a film
loaded.
[0008] The II is also used for fluoroscopic radiographing of heart
or brain as well as for a fluoroscopic inspection of gastric. Since
the moving image radiographing exposes a patient to X rays for a
long time, it is necessary to reduce the dose of X rays per unit
time in radiographing. For this reason, an X-ray imaging apparatus
needs to be higher in sensitivity than that used for the still
image radiographing.
[0009] An FPD capable of both photographing a still image and
radiographing a moving image has been proposed in recent years.
Radiographing a moving image needs to ensure a high frame rate
unlike photographing a still image. In general, cardioangiography
requires a frame rate of 30 FPS depending on the part and the
purpose of radiographing, so that S/N is improved by using, for
example, a pixel binding method to further increase the frame
rate.
[0010] The FPD can generate such turbulence in a signal that a
certain noise quantity is superimposed on a line basis. This is
referred to as "line noise" and brings about a horizontal (in the
direction of a line) linear artifact illustrated in FIG. 23 to
significantly decrease image quality.
[0011] The line noise is most probably attributed to the following
reason; a generated noise gets into a driving signal output from a
driving circuit because switching elements are collectively
operated on a line basis or into a signal wiring for some reason,
and thereafter is transferred at the same time. The line noise is
liable to be generated also at the time of resetting the capacitors
of the signal wiring and the capacitive elements in a reading
circuit because the resetting is performed on a line basis. The
line noise can get into a signal from the driving circuit and
various power supplies (including GND) or it generates in an
adjacent appliance and gets into a signal through space. The line
noise getting into at the time of establishing a proper electric
potential, for example, immediately before the transfer of signal
electric charges is finished or resetting is finished is turned
into a line noise on a line basis.
[0012] In general, a random noise is known as one of noises
resulting from the graininess of an image. The noise is generated
by a shot noise resulting from the dark current of a sensor (a
radiation detecting element), a thermal noise of a switching
element, a thermal noise generated in the resistance of a drive
wiring or a signal wiring and thermal noise from the operational
amplifier in a reading circuit. The line noise significantly
degrades image quality if the image is formed on a line basis as
illustrated in FIG. 23. If the line noise is generated not
singularly, as illustrated in FIG. 23, but randomly also on a line
basis, the relationship between the standard deviation G(R) of the
random noise and the standard deviation .sigma.(L) of the line
noise can be experientially .sigma.(L)=.sigma.(R) 1/10 or less.
That is to say, the line noise is extremely conspicuous on an image
and is very difficult to reduce. Particularly in the moving image
radiographing, a little dose of X rays produces a problem in that
the line noise is liable to be conspicuous. For example, the
following is cited as document on conventional art related to line
noise on an imaging apparatus. Japanese Patent Application
Laid-Open No. 2004-007551 discloses an imaging apparatus which is
provided with a line noise detecting unit for detecting the
existence of a line noise in the imaging output of a
two-dimensional area sensor stored in a memory circuit and
calculates the output quantity of the line noise to remove the line
noise from the imaging output. Furthermore, U.S. Pat. No. 6,734,414
discloses an imaging apparatus in which drive wirings are not
connected to pixels on a line basis, but randomly connected to
prevent a horizontal linear line noise from being generated as
illustrated in FIG. 20.
SUMMARY OF THE INVENTION
[0013] In Japanese Patent Application Laid-Open No. 2004-007551,
the output of the line noise is calculated from an average of line
output. However, particularly in the X-ray imaging apparatus with
an area of as large as 40 cm.times.40 cm, the line noises generated
on a line basis probably have shading and show an inappropriate
correction value as a line noise quantity to be corrected. Using a
calculation method taking the above into consideration causes a
problem that a real-time correction is difficult if it takes a long
time to perform calculation. In addition, a complicated algorithm
increases a burden to apparatus development and a cost.
[0014] In U.S. Pat. No. 6,734,414, since the drive wiring is
randomly connected, output signals are irregular and the output
signals need to be rearranged at a processing circuit of a rear
stage, consuming more time for processing the output signals and
leading to increase in the cost of apparatus configuration.
Furthermore, the connection of the drive wirings is complicated,
which may lower production yield to increase production cost.
[0015] That is to say, it has been difficult for the conventional
art to realize reducing an extremely conspicuous line noise
generated on an image without a substantial increase in cost and
with a relatively simple configuration. Especially in a moving
image radiographing (fluoroscopy) mode with a little dose of X ray
quantity, it has been very difficult to reduce the line noise with
a relatively simple configuration.
[0016] The present invention has been made in view of the problems
and has its purpose to provide a radiation imaging apparatus and a
radiation imaging system which realize reducing an extremely
conspicuous line noise generated on an image with a relatively
simple configuration.
[0017] The radiation imaging apparatus according to the present
invention includes a radiation detecting unit in which pixels
including the radiation detecting elements converting incident
radiation into electric charges are arranged two-dimensionally, a
control unit performing such a state control that a first pixel in
the radiation detecting unit is made senseless state so that an
electric charge generated in a first radiation detecting element
according to incident radiation cannot be taken out of the first
pixel and a second pixel different from the first pixel is made
sensible state so that an electric charge generated in a second
radiation detecting element according to incident radiation can be
taken out of the second pixel group and a signal processing unit
performing a subtraction processing such that the electric signal
read out from the second pixel made senseless state is subtracted
from the electric signal read from the first pixel made sensible
state according to the state control by the control unit. The
radiation imaging system according to the present invention is
provided with the radiation imaging apparatus and a radiation
source which radiates the radiation imaging apparatus with
radiation.
[0018] According to the present invention, an extremely conspicuous
line noise generated on an image can be reduced with a relatively
simple configuration. Furthermore, according to the present
invention, particularly in the moving image radiographing, reading
the addition of the pixel signals increases a frame rate and signal
quantity thereof, enabling generating a high-speed moving image
which is low in line noise. In addition, only a single radiation
imaging apparatus enables both still and moving image
radiographing. The present invention achieves an effect that
reduces the line noise without increasing cost.
[0019] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a schematic block diagram of a radiation imaging
apparatus according to a first embodiment.
[0021] FIG. 2 is a schematic circuit diagram of the radiation
imaging apparatus according to the first embodiment.
[0022] FIG. 3 is a circuit diagram illustrating an internal
configuration of a drive circuit in FIG. 2.
[0023] FIG. 4 is a timing chart illustrating an example of a first
operation of the drive circuit (shift register circuit unit) in
FIG. 3.
[0024] FIG. 5 is a timing chart illustrating an example of a second
operation of the drive circuit (shift register circuit unit) in
FIG. 3.
[0025] FIG. 6 is a timing chart illustrating an example of a third
operation of the drive circuit (shift register circuit unit) in
FIG. 3.
[0026] FIG. 7 is a circuit diagram illustrating an internal
configuration of a reading circuit in FIG. 2.
[0027] FIG. 8 is a timing chart illustrating an example of
operation of the radiation imaging apparatus according to the first
embodiment.
[0028] FIG. 9 is a circuit diagram illustrating an internal
configuration of a signal processing circuit in FIG. 2.
[0029] FIG. 10 is a timing chart illustrating an example of
operation of the radiation imaging apparatus according to a second
embodiment.
[0030] FIG. 11 is a sequence chart illustrating an example of
operation of still and moving image radiographing in the radiation
imaging apparatus according to the second embodiment.
[0031] FIG. 12 is a schematic circuit diagram of a radiation
imaging apparatus according to a third embodiment.
[0032] FIG. 13 is a timing chart illustrating an example of
operation of the radiation imaging apparatus according to the third
embodiment.
[0033] FIG. 14 is a timing chart illustrating an example of
operation of a signal processing circuit according to the third
embodiment.
[0034] FIG. 15 is a schematic circuit diagram of the radiation
imaging apparatus according to a fourth embodiment.
[0035] FIG. 16 is a schematic circuit diagram of a radiation
imaging apparatus according to a fifth embodiment.
[0036] FIG. 17 is a timing chart illustrating an example of a first
operation of the radiation imaging apparatus according to the fifth
embodiment.
[0037] FIG. 18 is a timing chart illustrating an example of a
second operation of the radiation imaging apparatus according to
the fifth embodiment.
[0038] FIG. 19 is a timing chart illustrating an example of
operation of the radiation imaging apparatus according to a sixth
embodiment.
[0039] FIG. 20 is a circuit diagram illustrating an internal
configuration of a reading circuit of a radiation imaging apparatus
according to a seventh embodiment.
[0040] FIG. 21 is a schematic circuit diagram of the radiation
imaging apparatus according to the seventh embodiment.
[0041] FIG. 22 is a timing chart of the radiation imaging apparatus
according to the seventh embodiment.
[0042] FIG. 23 is an example of an image on which line noise is
superimposed.
DESCRIPTION OF THE EMBODIMENTS
[0043] An exemplary embodiment to which the present invention is
applied is described in detail below with reference to the
drawings. In the present embodiment, an example in which X rays are
used as a radiation is described, however the present invention
does not limit the radiation to the X rays, but may include the
other radiations such as, for example, alpha, beta and gamma
rays.
First Embodiment
[0044] FIG. 1 is a schematic block diagram of a radiation imaging
apparatus according to a first embodiment.
[0045] The radiation imaging apparatus according to the first
embodiment includes a read unit 1102, drive unit 1103, radiation
detecting unit 1104, control unit 1150, signal processing unit 1160
and sensor bias supply unit (voltage supply unit) 1170.
[0046] The radiation detecting unit 1104 includes radiation
detecting elements, switch elements, drive wirings and signal
wirings and detects incident radiations such as X rays to convert
them into signal charges. The drive unit 1103 drives the switch
elements of the radiation detecting unit 1104 when electric signals
based on signal charges in the radiation detecting elements of the
radiation detecting unit 1104 are read. The read unit 1102 reads
the electric signals based on the signal charges in the radiation
detecting elements of the radiation detecting unit 1104.
[0047] The signal processing unit 1160 provides various processes
for the electric signals read by the read unit 1102 to generate
image data. While a signal processing unit includes the read unit
1102 and the signal processing unit 1160 in the present invention,
the signal processing unit may include other circuit elements such
as, for example, a memory. The sensor bias supply unit 1170
supplies the radiation detecting elements of the radiation
detecting unit 1104 with sensor bias. The control unit 1150
controls the read unit 1102, drive unit 1103, radiation detecting
unit 1104, signal processing unit 1160 and sensor bias supply unit
1170 to totally control the operation of the radiation imaging
apparatus.
[0048] FIG. 2 is a schematic circuit diagram of the radiation
imaging apparatus according to the first embodiment and illustrates
a detailed example of the block diagram in FIG. 1. In FIG. 2, 36
(six times six) pixels are illustrated to simplify the description
hereinafter.
[0049] The radiation detecting elements Si-1 to S6-6 convert
incident radiations into electric charges. The radiation detecting
element of the indirect type is formed by amorphous silicon and
that of the direct type by amorphous selenium. The radiation
detecting elements S1-1 to S6-6 are biased by a sensor bias supply
1501. Switch elements T1-1 to T6-6 are provided corresponding to
the radiation detecting elements respectively and transfer the
electric signals according to the electric charges on the
corresponding radiation detecting elements to the outside. The
switch elements T1-1 to T6-6 are typically formed by
thin-film-transistor (TFT) using amorphous silicon.
[0050] Drive wirings G1 to G6 are wirings to drive the switch
elements T1-1 to T6-6. Signal wirings M1 to M6 are wirings to read
electric signals in the radiation detecting elements through the
switch elements T1-1 to T6-6. The drive wirings G1 to G6 are driven
by the drive unit mainly formed of a shift register circuit 1103.
The signal wirings M1 to M6 are connected to the read unit 1102 to
read the electric signals in the radiation detecting elements. The
radiation detecting elements S1-1 to S6-6, the switch elements T1-1
to T6-6, the drive wirings G1 to G6 and the signal wirings M1 to M6
are collectively referred to as "radiation detecting unit" 1104. In
other words, pixels each including one radiation detecting element
and one switch element are two-dimensionally arranged in the
radiation detecting unit 1104.
[0051] The radiation detecting element of the indirect type
described above includes a phosphor (not shown) which converts
incident radiation into light and a photoelectric conversion
element which converts light converted by the phosphor into an
electric charge. The photoelectric conversion element is formed of
about 1-.mu.m thick semiconductor thin film containing as a main
ingredient amorphous silicon. The phosphor is arranged in such a
position as to be substantially brought into contact with the
photoelectric conversion element and containing as a main
ingredient any one of, for example, Gd.sub.2O.sub.2S,
GD.sub.2O.sub.3 and CsI.
[0052] On the other hand, the radiation detecting element of the
direct type described above contains as a main ingredient any one
of, for example, lead iodide, mercuric iodide, selenium, cadmium
telluride, gallium arsenide, gallium phosphide, zinc sulfide and
silicon. In this case, the radiation detecting element needs to be
500 .mu.m to 1000 .mu.m thick because it needs to absorb X
rays.
[0053] The radiation detecting elements are connected to a first
bias line VS1 (1111) or a second bias line VS2 (1112). In FIG. 2,
the radiation detecting elements in the even columns from the left
are connected to the first bias line VS1 (1111) and those in the
odd columns are connected to the second bias line VS2 (1112).
[0054] The sensor bias supply unit 1170 includes a first power
source unit 1171 which supplies bias to the radiation detecting
elements through the first bias line VS1 and a second power source
unit 1172 which supplies bias to the radiation detecting elements
through the second bias line VS2. The first power source unit 1171
is provided with a first switch 1109 which changes over from a
power source 1101 to GND or vice versa according to control from
the control unit 1150. The radiation detecting elements in the even
columns are supplied with bias voltage through the first bias line
VS1 according to the changeover. The second power source unit 1172
is provided with a second switch 1110 which changes over from a
power source 1100 to GND or vice versa according to control from
the control unit 1150. The radiation detecting elements in the odd
columns are supplied with bias voltage through the second bias line
VS2 according to the changeover. The power sources 1100 and 1101
may supply the same voltage.
[0055] The power sources 1100 and 1101 supply the radiation
detecting elements with bias and then the radiation detecting
elements generate electric charges according to the dose of the
incident radiation. This state is referred to as the "sensible
state" of the radiation detecting element. The connection of the
bias line to GND by the first switch 1109 or the second switch 1110
causes the radiation detecting elements not to generate electric
charges even if the radiation detecting elements are radiated with
radiation. This state is referred to as the "senseless state" of
the radiation detecting element.
[0056] Where, in the present invention, the "sensible state" of the
radiation detecting element refers to a state where an electric
charge generated in the radiation detecting element according to
the dose of the incident radiation can be taken out of the
radiation detecting element. On the other hand, the "senseless
state" of the radiation detecting element refers to a state where
an electric charge generated in the radiation detecting element
according to the dose of the incident radiation cannot be taken out
of the radiation detecting element. In other words, the "sensible
state" of the radiation detecting element refers to a state where
an electric signal based on the electric charge generated in the
radiation detecting element according to the dose of the incident
radiation can be read by a read circuit. On the other hand, the
"senseless state" of the radiation detecting element refers to a
state where only an electric signal not based on an electric charge
generated in the radiation detecting element according to the dose
of the incident radiation can be read by a read circuit. In the
first embodiment, supplying the radiation detecting element with a
voltage relative to GND (a first voltage) or 0 V makes the
radiation detecting element senseless state. More specifically, the
electrodes of the radiation detecting element are made
substantially little different in electric potential therebetween
to recombine electron hole pairs generated in the radiation
detecting element not to take out electric charges from the
radiation detecting elements, thereby enabling reading only
electric signals not based on electric charges. In the present
embodiment, although a voltage relative to GND is applied across
the radiation detecting elements to make the radiation detecting
elements senseless state, a forward bias may be applied across the
electrodes of the radiation detecting elements. In the first
embodiment, a bias voltage (a second voltage) is applied across the
radiation detecting elements by the power sources 1100 and 1101 to
make the radiation detecting elements sensible state. More
specifically, a reverse bias is applied across the electrodes of
the radiation detecting elements not to recombine the electron hole
pairs generated in the radiation detecting elements, thereby
enabling the electric charges to be taken out from the radiation
detecting elements.
[0057] In the present embodiment, as illustrated in FIG. 2, the
groups of the senseless state radiation detecting elements (groups
of first radiation detecting elements) are set in the even columns
and the groups of the sensible state radiation detecting elements
(groups of second radiation detecting elements) are set in the odd
columns. That is to say, the control unit 1150 controls the
changeover of the first and the second switch 1109 and 1110 to
provide such a state control as to make the radiation detecting
elements in the even columns senseless state and those in the odd
columns sensible state in the radiation detecting unit 1104.
[0058] The read unit 1102 reads the electric signals of the
radiation detecting elements S1-1 to S6-6 in the radiation
detecting unit 1104 according to the drive signals from the drive
unit 1103 and control from the control unit 1150. Based on the
control of the control unit 1150, the signal processing unit 1160
performs a subtraction processing in which the electric signals
read from the senseless state radiation detecting elements by the
read circuit unit 1102 are subtracted from the electric signals
read from the sensible state radiation detecting elements by the
read circuit unit 1102 to generate image data.
[0059] In an example of FIG. 2, although the groups of the
radiation detecting elements in the even columns are made senseless
state and the groups of the radiation detecting elements in the odd
columns are made sensible state, contrary to the above, the groups
of the radiation detecting elements in the odd columns can be made
senseless state and the groups of the radiation detecting elements
in the even columns are made sensible state. In that case, the
control unit 1150 throws the first switch 1109 to the position of
the power source 1101 and the second switch 1110 to the position of
GND. For example, if the radiation imaging apparatus is installed
in a good environment where line noise is little observed, the
radiation detecting elements do not always need to be made
senseless state to remove line noise. In that case, the radiation
detecting elements both in the odd columns and in the even columns
can be made sensible state. In that case, the control unit 1150
throws the first switch 1109 to the position of the power source
1101 and the second switch 1110 to the position of the power source
1100. Thus, the use of such a configuration as to switch a bias
applied across the radiation detecting elements allows providing a
good image high in resolution without reduction in the number of
effective pixels with all the groups of the radiation detecting
elements made sensible state if the senseless state radiation
detecting elements are not needed.
[0060] FIG. 3 is a circuit diagram illustrating an internal
configuration of the drive unit 1103 in FIGS. 1 or 2. The drive
unit 1103 includes a shift register circuit formed of D flip flops
1201, AND elements 1202 and level shift circuit 1203 as illustrated
in FIG. 3. The drive unit 1103 is controlled by three control
signals OE, SIN and Sclk. In general, the D flip flop 1201 and AND
element 1202 are digital circuits, of which input and output
voltages are related to a process for fabricating the above
elements. In general, an input and output voltages of High logic
have been 5 V system, however, nowadays a device operating at a
3.3-V or lower system appears because of recent demand for a lower
power consumption and development in process technique. In general,
however, the switching elements of the radiation detecting unit
1104 are containing as a main ingredient amorphous silicon, so that
the drive voltage can be 5 V or higher at least in a current
technique. For that reason, the level shift circuit 1203 applies a
drive voltage matching with characteristic of the amorphous silicon
TFT.
[0061] FIG. 4 is a timing chart illustrating an example of a first
operation of the drive circuit (shift register circuit unit) 1103
in FIG. 3. In FIG. 4, drive signals each being shifted by one step
are output to the drive wirings G1 to G6.
[0062] FIG. 5 is a timing chart illustrating an example of a second
operation of the drive circuit (shift register circuit unit) 1103
in FIG. 3. In FIG. 5, drive signals are simultaneously output into
the drive wirings G1 and G2, then the shift register shifts the
drive signals by two steps and simultaneously outputs drive signals
to the drive wirings G3 and G4, the shift register further shifts
the drive signals by two steps and simultaneously outputs the drive
signals to the drive wirings G5 and G6. This operation purposes to
bind pixels on a line basis (the number of binding pixels n=2), at
this point, the pixel pitch is twice as coarse as the above case
and the drive period is halved.
[0063] FIG. 6 is a timing chart illustrating an example of a third
operation of the drive circuit (shift register circuit unit) 1103
in FIG. 3. In FIG. 6, drive signals are simultaneously output into
the drive wirings G1, G2 and G3, then the shift register shifts the
drive signals by three steps and simultaneously outputs the drive
signals into the drive wirings G4, G5 and G6. This operation
purposes to bind pixels on a line basis (the number of binding
pixels n=3), at this point, the pixel pitch is three times as
coarse as the above case and the drive period is reduced to a
third.
[0064] FIG. 7 is a circuit diagram illustrating an internal
configuration of the read unit 1102 in FIG. 2. Operational
amplifiers A1 to A6 each functioning as an integrator include
capacitive elements CF1 to CF6 respectively as illustrated in FIG.
7. Switch elements SW1 to SW6 reset integral charges of the
capacitive elements CF1 to CF6 respectively by a control signal RC.
The capacitive elements C1 to C6 function to sample and hold the
signals of the operational amplifiers A1 to A6. Turning on switch
elements Sn1 to Sn6 causes the capacitive elements to sample and
hold the signals.
[0065] The switch elements Sn1 to Sn6 are turned on and off by a
control signal SMPL. Buffer amplifiers B1 to B6 serve to correctly
transfer the signal electric potentials of the capacitive elements
C1 to C6. The control signals from a shift register 1301 are
applied across switch elements Sr1 to Sr6 to transform the output
of the buffer amplifiers B1 to B6 from parallel signals to series
signals to be output through an amplifier 1302.
[0066] FIG. 8 is a timing chart illustrating an example of
operation of the radiation imaging apparatus according to the first
embodiment.
[0067] The operation on the first line is described first. The
signal charges photoelectrically converted by the radiation
detecting elements S1-1 to S1-6 in the first line are output to the
operational amplifiers A1 to A6 via the signal wirings M1 to M6
respectively with the switch elements T1-1 to T1-6 in the first
line turned on by the control signal to the drive wiring G1
(transfer operation). As a result, the respective signal charges
output to the operational amplifiers A1 to A6 are stored in the
capacitive elements CF1 to CF6. After that, the input of the
control signal SMPL collectively transfers the stored signal
charges to the capacitive elements C1 to C6 for sample and hold
respectively. The sequential input of the control signal from the
shift register 1301 into the switch elements Sr1 to Sr6 rearranges
the signal charges in the capacitive elements C1 to C6 from
parallel data to time-sequence series data to be output in the form
of an analog signal for one line (series conversion operation).
[0068] In the next place, the operation on the second line is
described. According to the timing chart in FIG. 8, after the
signal charges in the radiation detecting elements in the first
line have been sampled and held in the capacitive elements C1 to C6
by the control signal SMPL, the next transfer operation is enabled
for the signal charges in the radiation detecting elements in the
second line. In other words, the capacitive elements CF1 to CF6 are
reset by the control signal RC, thereafter, the drive wiring G2
performs the above transfer operation, and subsequently the
foregoing series conversion operation is conducted. Thus, the same
operations are repeated in the third line, fourth line, . . . and
n-th line. That is, in the circuit in FIG. 20, the existence of a
sample-and-hold circuit enables the transfer operation in n-th line
and the series conversion operation in n+1-th line to be performed
simultaneously.
[0069] In FIG. 8, Vout representing the output of an analog signal
from the read circuit unit 1102 is output every two pixels. This is
because the analog signal is output based on the control in which
the radiation detecting elements in the odd columns are made
sensible state and those in the even columns are made senseless
state by the control unit 1150.
[0070] In FIG. 8, a superimposed portion 310 of a so-called line
noise where a certain noise quantity is superimposed on a line
basis exists in the output signals (Vout) in the radiation
detecting elements S5-1 to S5-6 in the fifth line. This shows a
state where line noise equal in quantity is superimposed on pixels
in the sensible state odd columns and pixels in the senseless state
even columns. The line noise is subjected to a subtraction process
in the signal processing unit 1160.
[0071] FIG. 9 is a circuit diagram illustrating an internal
configuration of the signal processing circuit 1160. An analog
signal rearranged from parallel data to series data in the read
circuit unit 1102 and output through the amplifier 1302 of the
final stage is input into the signal processing circuit 1160. A
switch 2204 and a capacitive element 2206 sample and hold the
electric signal of the senseless state radiation detecting elements
and a switch 2205 and a capacitive element 2207 sample and hold the
electric signal of the sensible state radiation detecting elements.
For example, as illustrated in FIG. 2, when the radiation detecting
elements in the odd columns are sensible state and those in the
even columns are in senseless state, the signals in the odd and the
even columns are alternately input, so that the switches 2204 and
2205 are alternately turned on in synchronization therewith.
[0072] The electric signals of the sensible state radiation
detecting elements sampled and held in the capacitive element 2207
and the electric signals of the senseless state radiation detecting
elements sampled and held in the capacitive element 2206 are input
into an amplifier 2201 through buffer amplifiers 2203 and 2202
respectively. Setting the resistance of four resistors illustrated
in FIG. 9 around the amplifier 2201 to the same value allows the
amplifier 2201 to function as a differential amplifier. That is to
say, the differential amplifier 2201 performs a subtraction process
in which the electric signals of the senseless state radiation
detecting elements sent from the buffer amplifier 2202 are
subtracted from the electric signals of the sensible state
radiation detecting elements sent from the buffer amplifier 2203.
In other words, the electric signals of the senseless state
radiation detecting elements in the even columns are subtracted
from the electric signals of the sensible state radiation detecting
elements in the odd columns in such a manner that the electric
signals of the radiation detecting elements in the second column
are subtracted from those of the radiation detecting elements in
the first column in the same line and also the electric signals of
the radiation detecting elements in the fourth column is subtracted
from those of the radiation detecting elements in the third column
in the same line.
[0073] The output of the differential amplifier 2201 is input into
an AD converter 2220 in which an analog signal is converted into a
digital signal to form an image data. The signal processing
described above enables canceling the line noise superimposed on
the output signals (Vout) in the radiation detecting elements in
the fifth line in FIG. 8.
[0074] As in the present embodiment, when the radiation detecting
elements in the odd columns are made sensible state and the
radiation detecting elements in the even columns are made senseless
state, the finally obtained output signals include signals each
having one signal per two pixels. For this reason, the pitch
(sampling pitch) between pixels of the radiation detecting elements
arranged two-dimensionally is doubled in the direction of the line.
That is, for example, in the above case, pixels arranged at a pitch
of 160 .mu.m are read as those arranged at a pitch of 320 .mu.m as
far as the line direction (horizontal direction) is concerned.
[0075] A switch 2250 of the signal processing unit 1160 is a bypass
switch for directly inputting an analog signal into the AD
converter 2220 not through the sample-and-hold circuit and the
differential amplifier 2201. For example, in FIG. 2, the radiation
detecting elements do not need to be made senseless state by the
control unit 1150, but all the radiation detecting elements
(pixels) can be made sensible state. For example, if the radiation
imaging apparatus is installed in a good environment where line
noise is little observed, the senseless state radiation detecting
elements do not always need to be made senseless state to remove
line noise. At this point, the control unit 1150 turns on the
switch 2250 to directly input the output signal from the read
circuit unit 1102 into the AD converter 2220.
[0076] Although the sample-and-hold circuit and the differential
amplifier are used as a circuit example of the signal processing
unit 1160 in FIG. 9, other circuits may be used. For example, an
analog signal may be directly input into the AD converter and
stored in a memory circuit (not shown) and then a digital data may
be subjected to the foregoing subtraction process on hardware or
software using a computer.
Second Embodiment
[0077] FIG. 10 is a timing chart illustrating an example of
operation of the radiation imaging apparatus according to a second
embodiment.
[0078] In the second embodiment, as is the case with the first
embodiment, the radiation detecting elements in the odd columns are
made sensible state and the radiation detecting elements in the
even columns are made senseless state by the control of the control
unit 1150. Thus, also in FIG. 10, Vout representing the output of
the analog signal from the read circuit unit 1102 is output every
other pixel or only the signals in the radiation detecting elements
in the odd columns are output. As illustrated in FIG. 5, in the
second embodiment, the drive circuit (shift register circuit unit)
1103 provides such a control as to simultaneously input drive
signals into two drive wirings. This causes the read circuit unit
1102 to read the addition of the electric signals in the first and
the second line, the addition of the electric signals in the third
and the fourth line and the addition of the electric signals in the
fifth and the sixth line.
[0079] The use of the signal processing circuit 1160 illustrated in
FIG. 9 doubles a sampling pitch both in the line direction and in
the column direction. In other words, pixels arranged at a pitch of
160 .mu.m are read as those arranged at a pitch of 320 .mu.m in the
direction of line (horizontal direction), which means that pixels
are driven at a pitch of 320 .mu.m in the direction of column
(vertical direction). For the direction of column, the electric
signals of two pixels in each odd column are added and output.
Repeating the timing chart in FIG. 5 provides a moving image
radiographing. In this case, the read time of one frame is halved
as compared with that in the timing chart illustrated in FIG. 3.
This means that the frame rate of the moving image radiographing
can be doubled.
[0080] An application of the second embodiment is described below.
FIG. 11 is a sequence chart illustrating an example of operation of
still and moving image radiographing in the radiation imaging
apparatus according to the second embodiment.
[0081] In the moving image radiographing mode, when an image needs
to be recorded while a read operation is being performed at a
double sampling pitch in the direction of both line and column as
illustrated in FIG. 10 (fluoroscopic state), the moving image
radiographing mode is transferred to the still image radiographing
mode and the image is read at a normal sampling pitch. For the
moving image radiographing mode, the dose of incident radiation
(the quantity X ray) is small, so that radiographing is performed
at an increased frame rate while line noise is being reduced. For
the still image radiographing mode, radiographing is performed at a
high resolution.
[0082] More specifically, in the moving image radiographing mode,
the control unit 1150 performs a control in which a part of the
radiation detecting elements are made senseless state and the other
radiation detecting elements except the part thereof are made
sensible state in the radiation detecting unit 1104. Based on the
control of the control unit 1150, the signal processing unit 1160
performs a subtraction processing in which the electric signals
read from the senseless state radiation detecting elements by the
read circuit unit 1102 are subtracted from the electric signals
read from the sensible state radiation detecting elements by the
read circuit unit 1102 to generate image data.
[0083] On the other hand, in the still image radiographing mode,
the control unit 1150 performs a such control that all the
radiation detecting elements in the radiation detecting unit 1104
are made sensible state and the above subtraction process is not
performed in the signal processing unit 1160. Although FIG. 11 is a
timing chart starting in the fluoroscopic mode (FIG. 10) and ended
in the still image radiographing mode, modes may be repeated from
the fluoroscopic mode to the still image mode, from the still image
mode to the moving image mode, and from the moving image mode to
the still image mode.
Third Embodiment
[0084] FIG. 12 is a schematic circuit diagram of a radiation
imaging apparatus according to a third embodiment. In FIG. 12, the
same composing elements as in FIG. 2 are given the same reference
characters. In addition, 36 (six times six) pixels are illustrated
to simplify the description hereinafter.
[0085] FIG. 12 is different from FIG. 2 in the connection of the
bias lines VS1 and VS2 to the radiation detecting elements in the
radiation detecting unit 1104. More specifically, in FIG. 12, the
first bias line VS1 (1111) is connected to the radiation detecting
elements S1-1 to S6-1 in the first column and the second bias line
VS2 (1112) is connected to the radiation detecting elements in the
second to the sixth columns. In FIG. 12, a voltage (first voltage)
relative to GND is applied across the radiation detecting elements
in the first column from the first power source unit 1171 and a
voltage (second voltage) relative to the power source 1101 is
applied across the radiation detecting elements in the second to
the sixth columns from the second power source unit 1172. In other
words, in the present embodiment, the control unit 1150 performs
such a control that only the radiation detecting elements in the
first column out of the radiation detecting elements in the
radiation detecting unit 1104 are made senseless state and the
radiation detecting elements in the other columns (or the second to
the sixth columns) are made sensible state.
[0086] FIG. 13 is a timing chart illustrating an example of
operation of the radiation imaging apparatus according to the third
embodiment. As can be seen from FIG. 13, in Vout representing the
output of the analog signals from the read circuit unit 1102, the
output of the signals in the radiation detecting elements in the
first column is nothing, and the output of the signals in the
radiation detecting elements in the second to the sixth columns
appear in the output for each line.
[0087] FIG. 14 is a timing chart illustrating an example of
operation of the signal processing unit 1160 according to the third
embodiment. The signal processing unit 1160 related to the third
embodiment is also the same in configuration as that illustrated in
FIG. 9 as is the case with the first embodiment. In this case, the
signals in the senseless state radiation detecting elements in the
first column are read before those of the sensible state radiation
detecting elements in the other columns in the series conversion
operation of the read circuit unit 1102, which permits the signal
processing unit 1160 to sample and hold. If not, the subtraction
process at which the present invention is aimed is not executed in
the signal processing unit 1160 in FIG. 9. In that case, the
signals of all the radiation detecting elements may be converted
from analog signals to digital signals, stored in a memory (not
shown) and then data from the memory may be subjected to a desired
signal processing in the signal processing unit 1160.
[0088] Then, also in the signal processing unit 1160 according to
the present embodiment, the electric signals of the senseless state
radiation detecting elements read by the read circuit unit 1102 are
subtracted from the electric signals of the sensible state
radiation detecting elements read by the read circuit unit 1102,
allowing the removal of line noise illustrated in FIG. 14.
[0089] In the present invention, the output signals of the
radiation detecting elements in the first column made senseless
state by the control unit 1150 are not image data, and, as a
result, the number of an effective pixels is reduced to 30 pixels
(six lines.times.five columns) from 36 pixels (six lines.times.six
columns) initially existing in the pixel area of the radiation
imaging apparatus. In this case, for example, pixel signals in the
second column adjacent to the first column may be used to perform
an interpolation process to display 36 pixels. For a medical X ray
imaging apparatus, an actual image area needs to be as large as 40
cm.times.40 cm to radiograph the chest of a human body, so that the
radiation detecting elements may be arranged at a pixel pitch of
200 .mu.m or less. For the radiation imaging apparatus with such a
large area, when only the pixels in the end column are made
senseless state, like the radiation imaging apparatus according to
the present embodiment illustrated in FIG. 12, the number of
columns is as many as 2000, so that the interpolation process does
not always need be performed. For example, if the radiation imaging
apparatus is installed in a good environment where line noise is
little observed, the senseless state radiation detecting elements
do not always need to be made senseless state to remove line noise.
In that case, the groups of the radiation detecting elements in the
first column can be also made sensible state. In addition, the
control unit 1150 throws the first switch 1109 to the position of
the power source 1101. Thus, the changeover of bias applied across
the radiation detecting elements allows all the radiation detecting
elements to be made sensible state if the senseless state radiation
detecting elements are not required, which enables acquiring images
excellent in resolution without decrease in the number of effective
pixels.
Fourth Embodiment
[0090] FIG. 15 is a schematic circuit diagram of a radiation
imaging apparatus according to a fourth embodiment. As is the case
with the first to the third embodiment, the radiation detecting
unit 1104 includes radiation detecting elements, switch elements,
drive wirings and signal wirings and functions to detect incident
radiation such as X rays and convert it into an electric signal.
The fourth embodiment illustrated in FIG. 15 is different from the
other embodiments (for example, in FIG. 1) in that both the drive
unit 1103 and the read unit 1102 are divided into plural units.
[0091] A medical X ray imaging apparatus needs the radiation
detecting unit 1104 having an image area of as much as 40
cm.times.40 cm or more to radiograph the chest of a human body, so
that it is desirable that the radiation detecting elements with a
pixel pitch of 200 .mu.m or less be two-dimensionally arranged. The
radiation imaging apparatus with such a large area requires 2000 or
more drive and signal wirings.
[0092] The drive unit 1103 has a shift register circuit including
integrated circuits (IC) typically containing as a main ingredient
crystal silicon fabricated in a semiconductor process. An
individual IC is TCP modules mounted on film containing as a main
ingredient polyimide and connected to the radiation detecting unit
1104 in which amorphous silicon semiconductor thin film is
deposited on a glass substrate.
[0093] As is the case with the drive unit 1103, the read unit 1102
includes large scale integrated circuits (LSI) which are more
sophisticated than ICs in the drive unit 1103. The LSIs are TCP
modules mounted on film containing as a main ingredient polyimide.
A plurality of the LSIs is connected to the radiation detecting
unit 1104. In the present embodiment, the control unit 1150 may
perform such a control that the senseless state and the sensible
state column are set in a column area of which each read unit 1102
takes charge to perform a subtraction process. For example, as
illustrated in FIG. 12, only one senseless state column may be set
among a plurality of sensible state columns continuously existing.
In that case, although image information related to the radiation
detecting elements in the column made senseless state lacks,
lacking information may be interpolated with the outputs of pixels
in the adjacent sensible state columns. Specifically, the outputs
of pixels in the adjacent two columns can be used as those of
pixels in the adjacent sensible state columns for the interpolation
process.
[0094] Various methods are conceivable how to make a radiation
detecting element senseless state and sensible state. For example,
in the first embodiment, the radiation detecting elements in every
odd columns and in every even columns are made sensible state and
senseless state respectively as schematically illustrated in FIG.
2, and in the third embodiment, the radiation detecting elements
only in the end column in the plane of the radiation detecting unit
1104 are made senseless state as schematically illustrated in FIG.
12. In the latter, if line noise is superimposed without being
deviated, it can be corrected in a long line with a length of, for
example, 40 cm. In the former, since the pixels adjacent to the
sensible state pixels are always made senseless state, line noise
is equally superimposed in quantity, so that it can be accurately
corrected, however, resolution is halved in the line direction. In
the present embodiment, the read unit 1102 is divided into plural
units. If only one column is made senseless state in respective
read units, an intermediate effect is brought about between FIGS. 2
and 12. In other words, line noise can be accurately corrected
without degradation in resolution in the line direction. If line
noise is not observed, the radiation detecting elements do not
always need to be made senseless state to remove line noise. In
that case, the radiation detecting elements which have been made
senseless state only in one column in each read unit can be made
sensible state. In that case, the control unit 1150 throws the
first switch 1109 to the position of the power source 1101. Thus,
the changeover of bias applied across the radiation detecting
elements allows all the radiation detecting elements to be made
sensible state if the senseless state radiation detecting elements
are not required, which enables acquiring images excellent in
resolution without decrease in the number of effective pixels.
Fifth Embodiment
[0095] FIG. 16 is a schematic circuit diagram of a radiation
imaging apparatus according to a fifth embodiment. In the radiation
imaging apparatus of the present embodiment, the radiation
detecting elements S1-1 to S6-6 of the radiation detecting unit
1104 are biased by the same sensor bias supply 1501. The radiation
imaging apparatus of the present embodiment is provided with a
first drive unit 1113 for driving the switches in the odd columns
and a drive unit 1123 for driving the switches in the even columns
as drive circuits for driving the switch elements T1-1 to T6-6.
[0096] The first drive unit 1113 drives the switches in the odd
columns on a line basis according to the control of the control
unit 1150 through the drive wirings G1 to G6. The second drive unit
1123 drives the switches in the even columns on a line basis
according to the control of the control unit 1150 through the drive
wirings G7 to G12.
[0097] FIG. 17 is a timing chart illustrating an example of a first
operation of the radiation imaging apparatus according to the fifth
embodiment. FIG. 17 illustrates the timing chart in a normal
reading operation for cases where the control unit 1150 does not
make the radiation detecting elements senseless state in the
radiation detecting unit 1104 and makes all the radiation detecting
elements sensible state. This normal reading operation is
conducted, for example, in a still image radiographing mode.
[0098] In the normal reading operation, as illustrated in FIG. 17,
the control unit 1150 controls the first and the second drive unit
1113 and 1123 so that drive signals are simultaneously supplied to
any one of pairs of drive wirings G1 and G7, G2 and G8, G3 and G9,
G4 and G10, G5 and G11, and G6 and G12.
[0099] FIG. 18 is a timing chart illustrating an example of a
second operation of the radiation imaging apparatus according to
the fifth embodiment. FIG. 18 illustrates the timing chart in a
reading operation for cases where the control unit 1150 makes the
radiation detecting elements in the odd columns sensible state and
the radiation detecting elements in the even columns senseless
state.
[0100] More specifically, in the reading operation illustrated in
FIG. 18, the control unit 1150 drives the first drive unit 1113 to
cause the drive wirings G1 to G6 to supply the drive signals and
prohibits the second drive unit 1123 from driving. This does not
operate the switch elements provided corresponding to the radiation
detecting elements in the even columns, so that the signal charges
stored in the radiation detecting elements are not transferred and
the electric potentials are read idly to make the radiation
detecting elements senseless state. In this case, for example, the
line noise is read which is superimposed when the capacitances CF1
to CF6 (not shown in FIG. 16) of the first stage amplifier of the
read unit 1102 are reset.
[0101] The signal processing unit 1160 in the present embodiment
also subtracts the electric signals of the senseless state
radiation detecting elements in the even columns read by the read
unit 1102 from the electric signals of the sensible state radiation
detecting elements in the odd columns read by the read unit 1102.
This enables the line noise to be removed.
[0102] In the present embodiment, the radiation detecting elements
in the odd columns in the radiation detecting unit 1104 are made
sensible state and the radiation detecting elements in the even
columns are made senseless state. Contrary to the above, the
radiation detecting elements in the odd columns can be made
senseless state and the radiation detecting elements in the even
columns are made sensible state. In that case, the control unit
1150 prohibits the first drive unit 1113 from driving and drives
the second drive unit 1123 to cause the drive wirings G7 to G12 to
supply the drive signals. The image obtained for cases where the
odd columns are made sensible state and the even columns are made
senseless state is halved in resolution of the column. Contrary to
the above, the image obtained for cases where the even columns are
made sensible state and the odd columns are made senseless state is
also halved in resolution of the column. However, the latter image
is read after the former has been read, doubling the read time,
which, however, enabling reading without degrading resolution of
the column. In addition, for example, only the radiation detecting
elements in the first column among the radiation detecting elements
in the radiation detecting unit 1104 can be made senseless state
and the radiation detecting elements in the other columns (or, the
second to the sixth column) can be sensible state. In that case, in
radiation imaging apparatus illustrated in FIG. 16, only the switch
elements in the sixth column are connected to the second drive unit
1123 and the switch elements in the other columns are connected to
the first drive unit 1113, thereby making only the radiation
detecting elements in the sixth column senseless state.
Sixth Embodiment
[0103] FIG. 19 is a timing chart illustrating an example of
operation of a radiation imaging apparatus according to a sixth
embodiment. The radiation imaging apparatus according to the sixth
embodiment is the same in configuration as that of the fifth
embodiment illustrated in FIG. 16. That is, the control unit 1150
drives the first drive unit 1113 and prohibits the second drive
unit 1123 from driving to make the radiation detecting elements in
the odd columns sensible state and the radiation detecting elements
in the even columns senseless state respectively.
[0104] As illustrated in FIG. 19, in the sixth embodiment, the
first drive unit 1113 performs such a control as to simultaneously
input the drive signals into two drive wirings. This enables the
read circuit unit 1102 to read the addition of the electric signals
in the first and the second line, the electric signals in the third
and the fourth line, and the electric signals in the fifth and the
sixth line.
[0105] The signal processing unit 1160 in FIG. 9 is used to
subtract the electric signals of the senseless state radiation
detecting elements in the even columns read by the read unit 1102
from the electric signals of the sensible state radiation detecting
elements in the odd columns read by the read unit 1102, enabling
line noise to be removed.
[0106] The use of the signal processing unit 1160 in FIG. 9 doubles
sampling pitch both in the line direction and in the column
direction. This means that pixels arranged at a pitch of 160 .mu.m
are read at a pitch of 320 .mu.m in the line direction (horizontal
direction) and driven at a pitch of 320 .mu.m in the column
direction (vertical direction). For the column direction (vertical
direction) in the odd columns, the addition of two pixels is
output. The repetition of the timing chart in FIG. 19 allows a
moving image radiographing. In that case, a time required for
reading one frame can be halved compared with the timing chart
illustrated in FIG. 18. This means that a frame rate in the moving
image radiographing can be doubled. The sixth embodiment can be
applied to the radiographing sequence both of a still and a moving
image radiographing illustrated in FIG. 11.
Seventh Embodiment
[0107] FIG. 20 is a circuit diagram of read unit of a radiation
imaging apparatus according to a seventh embodiment of the present
invention. The read unit in FIG. 20 is characterized in that a
control signal for resetting the integral capacitances CF1 to CF6
of the operational amplifiers A1 to A6 is separated into RC and
RC1. That is to say, in FIG. 20, the control signal RC1 resets the
integral capacitance CF1 of the integral amplifier connected to the
signal wiring M1 and the control signal RC resets the integral
capacitances CF2 to CF6 of the operational amplifiers A2 to A6
connected to the signal wirings M2 to M6.
[0108] FIG. 21 is an example of a radiation detecting unit
connected to the read unit. FIG. 21 is different from FIGS. 2 and
12 in that the bias line for biasing the radiation detecting
elements is not separated into plural systems. However, a radiation
detecting unit connected in the present embodiment may use the
radiation detecting unit in FIGS. 2 and 12 provided that the
electric potentials of the bias lines are set to be equal to each
other in each system. The present embodiment is characterized in
that the control lines RC and RC1 of the read unit are separately
provided to cause the read unit to form radiation detecting pixels
corresponding to the senseless state region.
[0109] The present embodiment enables the signal wiring Ml
corresponding to RC1 to be set at the senseless state region of the
column. FIG. 22 is a timing chart illustrating the operation in
FIG. 20. RC1 is turned on with RC1 superimposed on the drive
signals provided for the drive wirings G1 to G6 which turn on TFTS.
This allows the signal charges in the radiation detecting elements
corresponding to the column of the signal wiring M1 not to be
integrated by the integral capacitances CF1 but to be made
senseless state.
[0110] Turning on the control signal SMPL for sample-and-hold after
the control signal RC1 has been turned on causes the electric
charges of CF1 to CF6 to be sampled and held in the sample-and-hold
capacitors C1 to C6. At this point, as illustrated as Vout in FIG.
22, line noises getting into the signal wirings M1 to M6 and the
output terminals of the operational amplifiers A1 to A6 through the
power source line, GND line and space are sampled and held in
synchronization with the sample-and-hold signal. These noises are
separately subtracted and compensated by, for example, the
processing circuit illustrated in FIG. 9.
[0111] Incidentally, in the present embodiment, the control line of
the operational amplifier corresponding to the signal wiring M1 is
taken to be a separate system in the above description, however it
may be separated into an odd and an even system in
configuration.
[0112] In the timing chart in FIG. 22, while the control signal RC1
is so controlled as to be completely superimposed on the drive
signals which turn on the TFTs, it does not need to be completely
superimposed if the above control aims to operate as senseless
state region or to superimpose line noise.
[0113] In the embodiments according to the present invention, as
stated above, the senseless state of the radiation detecting
elements means a state where electric signals cannot be taken out
of the radiation detecting elements, in other words, it also means
a state where only line noise can be detected. In addition, as
stated above, the sensible state of the radiation detecting
elements means a state where electric signals can be taken out of
the radiation detecting elements, in other words, it also means a
state where line noise may be included in the electric signals of
the radiation detecting elements.
[0114] The radiation imaging system can be provided as other
embodiments according to the present invention. For example, the
radiation imaging system includes a system which has any of the
radiation imaging apparatus of the first to sixth embodiments and a
radiation source which emits radiation to the radiation imaging
apparatus through an object. This radiation imaging system also
enables achieving the above effect of the present invention.
[0115] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0116] This application claims the benefit of Japanese Patent
Application No. 2006-066089, filed Mar. 10, 2006, and Japanese
Patent Application No. 2007-008140, filed Jan. 17, 2007, which are
hereby incorporated by reference herein in their entirety.
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